<div class="form-group">
  <label class="col-xs-12 col-sm-4 control-label text-right">封面：</label>
  <div class="col-xs-12 col-sm-8">
    <fieldset class="field">
      <div>
        <div class="fileinput fileinput-new">
          <div class="fileinput-new thumbnail">
            <img class="default-img" [src]="imgUrl">
          </div>
          <div class="fileinput-preview fileinput-exists thumbnail"></div>
        </div>
      </div>
    </fieldset>
  </div>
</div>
